Machine tool holder unit

Abstract

An interchangeable machine tool holder unit for use in a machining apparatus for the support of a machining element, for example, a cutting bit, which includes an elongated rotary body adapted to be driven in one direction about the longitudinal axis thereof, a tool holder supported in end-to-end fashion by the rotary body for movement in a direction radially of the rotary body, an axially displaceable member axially displaceably carried inside the rotary body, and an indexing mechanism for causing the axially displaceable member to move in the axial direction each time the rotary body undergoes one complete rotation to permit the tool holder to move in the radial direction. During the continued rotation of the rotary body in one direction, the displaceable member is axially moved in response to each complete rotation of the rotary body, and the movement of the displaceable member results in a radial shift of the tool holder to permit the cutting bit to effect counterboring, drilling or cutting of a workpiece.

We claim: 
     
       1. An interchangeable machine tool holder unit for use in a machining apparatus for the support of a machine element, which comprises: a source of rotary drive;   a generally elongated rotary body having ends;   a means coupling one of said ends of the elongated rotary body to said source of rotary drive;   a tool holder including a first supporting means supporting the machining element at one end thereof opposite to the rotary drive coupling means;   a second supporting means provided in said rotary body supporting said tool holder for movement in a radial direction of said rotay body;   a displaceable member which is axially displaceably carried by said rotary body;   a first cam means transmitting the axial displacement of the displaceable member to the tool holder to move the latter in a direction radially of the rotary body; and   an indexing mechanism intermittently moving the displaceable member in the direction axially of the rotary body each time the rotay body undergoes one complete rotation driven by the source of rotary drive, said indexing mechanism comprising an exteriorly threaded rod supported by a third supporting means within the rotary body so as to extend in a direction radially of said rotary body, a toothed wheel member mounted on one end of the threaded rod for rotation together therewith, and an indexing cam mounted on the theaded rod for movement in a direction axially to the threaded rod, said indexing cam being movable axially of and along the threaded rod as the threaded rod is turned about the longitudinal axis thereof and said displaceable member being axially moved in response to the axial movement of the indexing cam.   
     
     
       2. A machine tool holder unit as claimed in claim 1, wherein said toothed wheel is connected to the threaded rod through a load-responsive, automatically releasable clutch operable to disengage the toothed wheel from the threaded rod in the event of the occurence of an overload imposed thereon. 
     
     
       3. A machine tool holder unit according to claim 1 or 2, further comprising a support barrel mounted on the rotary body, said support barrel including a drive transmitting means for turning the threaded rod a predetermined angle about the longitudinal axis thereof each time the rotary body undergoes one complete rotation. 
     
     
       4. A machine tool holder unit as claimed in claim 3, wherein said drive transmitting means includes a control means controlling the transmission of the rotary motion of the rotary body to the threaded rod. 
     
     
       5. A machine tool holder unit as claimed in claim 3, wherein said drive transmitting means comprises a drive pin carried by the support barrel for engagement with any one of the teeth of the toothed wheel, said threaded rod being turned each time the drive pin abuts one of the teeth of the toothed wheel. 
     
     
       6. A machine tool holder unit as claimed in claim 5, wherein said control means comprises a biasing spring member urging the drive pin to a retracted position where the drive pin is clear of the path of rotation of the toothed wheel, and an air supply means moving the drive pin against the biasing spring member to a projected position where the drive pin is ready to engage any one of the teeth of the toothed wheel. 
     
     
       7. A machine tool holder unit as claimed in claim 1, wherein the first cam means includes a follower member rigidly secured to the tool holder. 
     
     
       8. A machine tool holder unit as claimed in claim 1, wherein the first cam means includes a counter-wedge member adjustably supported by the tool holder for adjustment in a direction axially of the rotary body and in a direction both towards and away from the displaceable member. 
     
     
       9. A machine tool holder united as claimed in claim 1, further comprising a first roller bearing means interposed between the peripheral surface of the displaceable member and a bore in the rotary body in which the displaceable member is movably accommodated, and a second roller bearing means interposed between a cam face, defined in the displaceable member, and a mating cam face defined in a cam element forming a part of the first cam means and carried by the tool holder facilitating the relative sliding movement between the displaceable member and the cam element. 
     
     
       10. A machine tool holder unit as claimed in claim 9, wherein one end of the tool holder adjacent the rotary body has a connecting groove defined therein so as to extend in a direction radially thereof, and one end of the rotary body adjacent the tool holder has a mating projection formed therein so as to extend in a direction radially thereof, said mating projection being slidably received in the connecting groove to connect the tool holder and the rotary body together, and further comprising a third roller bearing means interposed between the mating projection and the connecting groove. 
     
     
       11. A machine tool holder unit as claimed in claim 10, wherein said groove is a dovetail groove and said mating projection is a dovetail projection having a cross sectional shape complementary to the cross sectional shape of the dovetail groove. 
     
     
       12. A machine tool holder unit as claimed in claim 10, wherein said groove is of a generally T-shaped cross section and said mating projection has a cross sectional shape complementary to that of the groove.